On my current layout I used a curved utility knife like John has shown and I’m sure Tom as well.  In the past, yes the dust was bad.  We plan to move once my mother-in-law passes; she lives across the road.  Depending on my age and health, (I’m closing in on 65) I may take parts of the Blackwater Canyon Line or scrap it and build new.  I like the foam and ply sandwich, Don.

The first foam only layout I saw was a modular HO at a show probably 25 years ago. They had glued enough layers together so it was about 8 inches thick.

It looks like GRJ and Mark answered my questions of cutting Homasote, mess-free. Thanks.  This topic reminds me of what an old timer HO master model railroader said in a seminar I caught yesterday while doing paperwork for real work:  The beauty of this hobby is there is no one right way of building a model railroad and everyone brings good ideas into the hobby.  Rigid Foam? Styrofoam? Spray Foam? Homasote? Plywood?  MDF? Masonite?  Ceiling tiles? Combinations?  All good.  Happy Friday, everyone.

You can use a clean 6" spackle knife for cutting 2" foam perfectly clean with out a mess.  Just score a line and repeatedly go over it with a tad more pressure with each pass.  You will find the angle which cuts best:

If you aremaking crumbs your angle is too high or too low.

This was for the late o scaler and quick draw gun slinger Pennsy K-4.   An off layout town scene.

That’s slick, Tom!

Tom -- that's essentially what I did, except that I sharpened the edge of the 'putty/spackling' knife (which was 3 or 4 inches wide across the end of the blade).  With the foil on the foam, I needed something sharp(er) to make the cuts through the foil, but using a straight edge to draw the blade along made short work of the cutting.  Seems to me you could use some sort of curved template to make those cuts - you just couldn't cut as deeply with a single stroke.

I set the module on the foam to scribe a slightly indented curved line by lightly dragging the knife.  Then, lifting the module off of the foam I proceeded to follow the scribe line repeatedly.  It takes about 5 passes to achieve a through cut.  When cutting like this I hold the knife so it can float in  my hand.  I let the line guide the knife I do not try to steer the knife by hand.

Cutting foam like this is second nature to me, I do a lot of foam fabrication so I recogonize it may take a few oops! to get comfortable with it.

I peel the skin off when ever I can.  If it does not peel clean my first pass is with a Airway #6 razor knife to break through the foil.  Then all the following cuts are with a 6" spackle knife.  I find a much smaller spackle knife does NOT have the curve shape necessary to cut foam in this fashion.

This is the same knife I use for cutting Homasote.  This is NOT a box cutter but rather almost a shaving quailty thin blade that will cut a finger to the bone before you feel it.

Change blades like they were free every 5 to 10 feet.  Five passes will go through 1/2" Homasote.

@Don Merz 070317 posted:

One thing I should come clean about is that the platform top is not just 2 inch foam. I made a "layer cake" of 3/8 inch plywood, 2 inch foam, another 3/8 inch plywood and another 2 inch foam. See pic. So my platform is very dense and pretty sound dead. I have no noise problem.

I call shenanigans!   You just blew you're own thread out of the water. You have 3/4" of plywood attached to foam.

I'd say that's a far cry from the thread title!

Styrofoam On A Platform--Not Plywood On 2x4's

I call double shenanigans!  Were you building a battleship?

Ahhh geez...I guess I got us all wrapped around the axle. Do I have a point? If so, what is it?

Just this: I have had big fun building my layout (mostly) with foam and Gorilla glue. The TOP of the platform is foam. The risers to lift the track up and around curves are all foam. The inner core of most of my scenery is foam (and that which isn't is bendable metal fencing, not wood).

It has been fast and relatively easy. When I have made mistakes or had an epiphany about a modification that I simply MUST have in my track plan, the foam has been simple to change--no saw required.

I have enjoyed working with the sheet foam. I think building the same thing with wood would not have been anywhere near as much fun.

The reason I used 3/8 inch plywood in foam sandwiches that make up my platform is because my benchwork is unconventional. My benchwork is a metal frame around the edges of the layout (see pic). There is exactly ONE LEG in the middle of each major section of the layout. All other layout legs are attached to the metal frame at the edges. You can look under the layout and see wide open spaces instead of a forest of legs and woodwork. But the metal frame benchwork is a one-off. It would be hard for anyone to replicate. I had the frame and I used what I had. Most folks would not have a huge, steel, bridal-show display frame laying around <grin>!

Finally, my opinion is that L-girder benchwork with 1x2's or whatever for legs is obsolete. It is time-consuming, costly (wood prices these days!), and far less flexible than a platform supporting foam risers, foam-topped flat spaces and foam scenery.

Don Merz

I was planning an around the wall layout for my 10 x 13 train room however it has become clear that the CEO loves the house but is not enamored with it's location so plans have shifted to a 4 x 8 tabletop layout.  To make quick work of it, use some idle on hand items and to keep it as light as possible I was thinking 2"foam, sandwiched between some 3/16' underlayment I have laying around like Don did.  The underlayment is just to give any screws required for track, accessories, what have you, something to bite into.  A 60" Samsonite folding table is going to be the base. Not being sure if this sandwich would be rigid enough to prevent flexing or sagging beyond the edges of the supporting table I'm thinking of a frame for it to "float" in like shown on page 1 of this thread.  My belief is this would be lightweight, easy up, easy dismantle and use some stuff taking up room in the garage.  I'll need to buy the foam and Lumber for the frame if that is necessary.  I figure to make the sandwich first throw it on the table and see if the frame is required.

Joe, that sounds like a good idea to try the sandwich first and go from there.  My Christmas layout is 2” foam on a folding banquet table.  I just slid some spare 2x4s under to support it for a short season.  With the cost of lumber, I used the 2x4s on the ‘permanent’ layout, so I’ll need to come up with other support if I set up the Christmas layout this year.

Coach Joe: My top layer is foam, not wood. To screw the track (or anything) into the foam, I mark where the screws would go and I push in a wall plug coated in Gorilla glue. I wait a few hours or overnight, then I can screw into the wall plug. It makes a solid connection and is not at all fragile. I did a thread on this forum about screwing into foam. It has pix and all. Please look that up if you want to consider that approach.

Don Merz

Richs09: I am going to try the sharpened spackling knife trick today! Good idea. I've been getting by with big, old kitchen knives found at thrift stores for a buck a boxfull. But those knives have too much give to them. The spackling blade should do the trick!

Don Merz

Don - it doesn't have to be razor-sharp.  I only sharpened one edge, first just using my fine grinding wheel, then cleaning it up with a flat file.  I may have made a few passes on my sharpening stone - I don't recall.

Rich

@gunrunnerjohn posted:

My one experience with 2" foam with track directly on it was fairly loud.  The foam is quite rigid and performs like a drumhead.  I have to say, my plywood and Homasote deck is very quiet.

@Avanti posted:

Sounds like a good plan. If you add a framework of 1x4 joists 18" (or less) on centers, I think you will find it a fine permanent solution--it will easily support your weight if needed.

I suppose the wood clad foam would be OK ..🤔.?...., but after seeing a post ( which I  can't locate now ) of what a shorted switch and foam can do to incinerate your dwelling .........well .....the plywood and Homasote seems to be the best solution.

Built a couple of these for our club’s portable layouts. 4’ x 8’.  Glued foam to very thin plywood (cheapest I could find).  Composite foam board/plywood is very strong.  Put in on a very light frame made of 1 x 4 and 1 x 2.  Track is tubular.  Put foam weatherstripping underneath (Inside) ties so track just barely floats above foamboard.  Track is held to foamboard with the two zip ties trick.  Track can be moved ever so slightly.  It is very quiet!  2 each  1 x 2 are attached to the bottom and are spaced such that they align to the edges of a standard banquet table (30”).  The layout is simply clamped to the tables.  Works great.  Very stiff and very light.

I am building my first layout. Small at 3x5 feet. I used 1x4s for the table and 2 inch foam pink foam board. Built in the garage, painted (executive order) and assembled base and top in the garage. The pink foam has a cheap paneling backing on the bottom to provide extra support. I can lean on it to do scenery and not punch through. Much lighter and as strong as 2x4 construction.

@gunrunnerjohn posted:

Foam shrinks that much?  I haven't seen that with our modular club, that's the first time I heard of that!

Foam does shrink, but it takes awhile.  Our club's modular layout has construction foam for removable mountains, and the shrinkage became noticeable after about 15 years or so.  I don't know if storing the layout in an uninsulated trailer contributed to the shrinkage.  The older club members think that it might have shrunk less had all sides been painted.

I have a 4x6 On30 layout that consists of 2" pink foam in a light wood frame.  The wood frame is for appearance, keeping everything together, and eliminating flex and protecting the edges when moving the layout.  The Bachmann track (which is similar to Lionel Fastrack) is fastened to the foam with Loctite Power Grab adhesive.  The track was completely assembled in place, screwed into the foam to maintain alignment, and fully tested.  Then a bead of Power Grab was put down along each edge of the track. (At that point, the screws are redundant.)  The bond is very strong, and I'm hoping that the adhesive will be fairly easy to remove from the track if/when I decide to tear it down and start over.

@CR Cole posted:

I am building my first layout. Small at 3x5 feet. I used 1x4s for the table and 2 inch foam pink foam board. Built in the garage, painted (executive order) and assembled base and top in the garage. The pink foam has a cheap paneling backing on the bottom to provide extra support. I can lean on it to do scenery and not punch through. Much lighter and as strong as 2x4 construction.

That looks exactly like mine (described above), except that I didn't bother with a panel backing, but it's probably a good idea.

@Mallard4468 posted:

Foam does shrink, but it takes awhile.  Our club's modular layout has construction foam for removable mountains, and the shrinkage became noticeable after about 15 years or so.  I don't know if storing the layout in an uninsulated trailer contributed to the shrinkage.  The older club members think that it might have shrunk less had all sides been painted.

Gets really hot in the trailers in the summer . 😥

I forgot about the paneling until I went to poke a hole through the foam for some wires. Took a few minutes to remember, duh, solid board under the foam! Senior moment! 😀

Not sure about the shrinkage issue. It is glued to the paneling, so that should help. God willing, I will report back in 15 years!

@Mallard4468 posted:

Foam does shrink, but it takes awhile.  Our club's modular layout has construction foam for removable mountains, and the shrinkage became noticeable after about 15 years or so.  I don't know if storing the layout in an uninsulated trailer contributed to the shrinkage.  The older club members think that it might have shrunk less had all sides been painted.

I used a lot of foam on my last layout built 14 years ago.  I am reusing a lot of that  foam and I've not seen any shrinkage.  But my foam has always been in climate controlled environments.  Most of the foam I use is 1/2" to 1".  Perhaps 2" foam is subject to this more?  And because of extreme temperatures?  Yet it is used primarily for exterior basement wall insulation so it seems to me that shrinkage would be minimal.

For what its worth, here's a link to a 2008 article in Model Railroader about foam shrinkage (or lack thereof):  http://cs.trains.com/mrr/f/11/t/139257.aspx

OTOH, just to confuse things slightly, the construction industry does report some shrinkage, to wit, here:  https://www.buildingscience.co...rinks_Correction.pdf but by my read, this is largely thermal expansion/contraction, as opposed to 'aging' under a fairly stable thermal environment.

I suppose one could look at what DOW and/or Owens Corning have to say on their websites...

Most of my 2nd level is on a blue foam base and foam support columns....and 26 years old. No discernable issue with shrinkage. I think the foam will be just fine for another 26 years.

Ok Rich, way too much to think about. Mine is in the house, so a stable environment. See the shabby and dilapidated thread, natural decay of things over time! 😄

@richs09 posted:

For what its worth, here's a link to a 2008 article in Model Railroader about foam shrinkage (or lack thereof):  http://cs.trains.com/mrr/f/11/t/139257.aspx

OTOH, just to confuse things slightly, the construction industry does report some shrinkage, to wit, here:  https://www.buildingscience.co...rinks_Correction.pdf but by my read, this is largely thermal expansion/contraction, as opposed to 'aging' under a fairly stable thermal environment.

I suppose one could look at what DOW and/or Owens Corning have to say on their websites...

The building science article says "all materials" expand and contract in extreme temperatures is the relevant statement here.  My professional experience in windows, doors and sunrooms tells me everything moves on the exterior of the building unless it is anchored below the frost line.  And the parts that are above the frost line still expand and contract.  However, unless you're building your layout outside to operate in 100 degree+ summers or -32 degree winters, you probably don't have to worry about foam shrinkage.

Rigid foam does not swell when it is exposed to indoor basement moisture like wood.  So if you're worried about your foam contracting, you ought to worry much more about your plywood or the frame of you tables drying out and shrinking or retaining moisture and swelling.   Most of us know the frustration of building lift bridges that join together perfectly.  And then they don't.   That's why we run dehumidifier(s) in the summer months.  

Okay, so I gave my Tri-Ply/foam sandwich a try.  Went with 2 inch foam for rigidity.  Glued leftover pieces of Tri-Ply to each side.  I figured the Tri-ply gives screws something to bite into and seeing Dallas Joseph's post about shorts and foam I think it was the right choice instead of gluing anchors into the foam whenever I need to screw something down.  The sandwich isn't as light as I had expected but I believe it is stiff enough that I won't need a frame.  It'll just lay on top of an old folding table.  Cleats in all 4 corners to prevent the lyout from sliding off the folding table.  So my new 4 x 8 railroad empire has finally begun.  I gave the surface and edges two coats of a sandy soil flat base coat.  I may add some brown shading with some spray paint to give the color some depth.

Joe, I like that foam sandwich, and the cleats to hold it on the table. Looking good!

Joe, I agree with Art!!

@coach joe posted:

Okay, so I gave my Tri-Ply/foam sandwich a try.  Went with 2 inch foam for rigidity.  Glued leftover pieces of Tri-Ply to each side.  I figured the Tri-ply gives screws something to bite into and seeing Dallas Joseph's post about shorts and foam I think it was the right choice instead of gluing anchors into the foam whenever I need to screw something down.  The sandwich isn't as light as I had expected but I believe it is stiff enough that I won't need a frame.  It'll just lay on top of an old folding table.  Cleats in all 4 corners to prevent

Joe,

I am not familiar with the term "Tri-ply" (except maybe for stainless steel).

Is it 5mm underlayment?

Thanks,

John

I'm curious about the glue you used in that caulk gun.  Would you mind sharing what kind of adhesive you used and did 1 tube do the job?  Looks great.  It reminds me of folks who have used solid core or even hollow core doors to build a layout tables in the magazines.

I am not familiar with the term "Tri-ply" (except maybe for stainless steel).

Is it 5mm underlayment?  Yes it is.

I'm curious about the glue you used in that caulk gun.  Loctite PL300 Foamboard Construction Adhesive.  3 tubes.

I gave my Tri-Ply/foam sandwich a try.  Went with 2 inch foam for rigidity.

Why would 2" of foam give you any more appreciable rigidity than the plywood?

It may give you some sound absorption, assuming  the track screws are not into the plywood, but I can't see why foam would add rigidity more so than the plywood.

A flitch plate relies on the steel ( Young' modulus is 29Mpsi), the surrounding wood allows nailing, but the steel plate is far more rigid than the surrounding wood (Young's modulus is 1.4 Mpsi).

This is also true of your Tri-Ply/foam sandwich Foam is .03Mpsi  compare to the plywood at 1.5 Mpsi;

Your plywood is 50 times stronger than the foam.

I like the tri-ply sandwich. Since you are overlapping the table you might consider running a board from the cleats on each end to lock down to the table with thumb screws. That way if you lean on the edge you don't tilt the sandwich and have it slide of the table! That is something that I know would happen to me!

As to cutting straight cuts in foam I use my table saw or chop saw.... surprisingly little mess and clean cuts. Curves have been a challenge but it worked out to make one side of my canyon

AlanRail, I went with foam over plywood for the weight.  Chose 2" foam instead of 1" for rigidity.  Sorry I didn't make that clear.  While the sandwich is heavier than I thought it would be I believe it is still lighter than 3/4" plywood.

Looks good, Coach - I don't think you'll have any problem with the overhang, but you could always attach a rough grade 1X2 or old wooden table leg at each corner for additional support.

Will you need to drill through the folding table top to run any wiring ?

I've been thinking about 2" foam for the Christmas layout. I am using old school O27 track. The layout is going to be flat I am going to make a riser, probably wood for the upper deck (the North Pole) with a single loop and room for a modest artificial tree with my train ornaments. The main loops on the first level will pass under the platform.

I want to run wires underneath to keep things neat, so I'd want it to be off the floor an inch or 2. Though just under the white felt/other (for the snow) is an option. I have a number of Lionel street lamps I want to anchor, plus block signals and semaphores for lights and action. A crossing gate or two. I also have a Passenger Stop Station which will use on the inside loop on the main level.

Can you put screws in the foam to hold things in place. Same for track a few screws here and there to hold the track in place.

So if I prop it up will that make it noisy? And can I run #4 x up to 2" screws into the foam?

Frank

Frank, I just use 1 3/4 paneling nail, the ones with the head, not finish nails, at a slight angle. Holds tight, even when I had to pull up track to get my switches fixed everything locked back tight. All my assemblies are nailed down to foam that way.

@CR Cole posted:

Frank, I just use 1 3/4 paneling nail, the ones with the head, not finish nails, at a slight angle. Holds tight, even when I had to pull up track to get my switches fixed everything locked back tight. All my assemblies are nailed down to foam that way.

1 3/4 paneling nails directly into the foam itself, not through a top board?

John